Methods of Manufacturing Formaldehyde-Free Molded Products and Related Parts

ABSTRACT

The present invention provides a moldable mixture containing large portion of agricultural fibers and small portion of a binding agent and a flow-promoting filler material. The moldable mixture is substantially free of formaldehyde, with low moisture content and high draw ratio. The present invention also provides methods of manufacturing molded products and related parts, based on the claimed moldable mixture. Molded products ( 830 ) and related parts such as runner ( 810 ) and plank ( 820 ) with light weight, high density and more complex profile are manufactured by the claimed methods including steps of providing required materials for a moldable mixture, mixing the provided materials to form a moldable mixture, shaking the moldable mixture in preparing for compression molding and compression molding the moldable mixture to form molded products and related parts.

TECHNICAL FIELD

The present invention relates to packaging materials and related methodsfor construction of the same. With greater particularity the presentinvention relates to moldable materials for use in the construction ofpallets and methods of producing the same. With even greaterparticularity the present invention relates to moldable materials andrelated methods of using the same for construction of pallets which aresubstantially free of formaldehyde.

BACKGROUND ART

A pallet is a flat transport structure made of either wood, plastic,paper, metal and composite material that can support a variety of goodsin a stable fashion while being lifted by any mobile pallet liftingdevice. The purpose of the pallet is to improve storage and productdistribution efficiency and to protect the product. Pallet servesequally as the interface between the packaged product and the roughnessof the product distribution environment which includes many differentvibrations and shocks during truck, rail or air transportation.

Today, it is estimated that there are more than one billion new palletsthat are produced yearly worldwide. It is estimated that more than 93%of the pallets produced are made of wood. Due to the use of wood as asource, the consumption of wood for making wood pallets is nowrecognized as part of the deforestation which is a major contributoryfactor to global warming. The compressed wood pallet that uses MelamineUrea Formaldehyde (MUF) or Urea Formaldehyde (UF) as the binder maycause health hazards according to the International Agency for Researchof Cancer. Other than the afore-mentioned environmental problems, woodpallets also carry risk of introduction and/or spread of quarantinepests. New guidelines named as “International Standards for RegulatingWood Packaging Material in International Trade” (ISPM 15) are set out togovern the use of wood packaging materials. Under the ISPM 15guidelines, all wood pallets need to be either heat treated or fumigatedso as to ensure that no living pests are being transported from onecountry to another. Unfortunately, not all types of wood can be heattreated and chemicals, especially methyl bromide, used for fumigationappears to cause health hazards.

Due to the afore-mentioned disadvantages of using wood packagingmaterials, alternative materials such as plastics, metal, compositematerials have been used. However, these packaging materials are neitherenvironmental friendly nor cost-effective. For example, the plasticpallet takes more than 100 years to be degraded. Plastic and metalpallets are also relatively more costly and heavier. As oil prices reachthe new highs, it is no longer cost-effective to use plastic and metalpallets, especially for one-way transportation of goods by air ascharges are more likely directed to the weight of packed cargo,including the weight of pallet.

Conventional open-molding process is mainly used for manufacturing offlat sheet or board. As there is no built-up wall along the parameter,the molded product usually requires trimming and has relatively lowdensity. Composite materials used in such process only require theaddition of low content binder without the use of filler material orflow promoter. However, the main disadvantages of open-molded productare that the profile of the molded product is limited to the flat sheetand usually with a standard size. The wastages from trimming the fouredges are also relatively high. It is not cost-effective in terms ofmaterial utilization.

Comparing with open-molding process, products produced by typicalclose-molding process have relatively higher density and can result in amore complex profile of the molded product. There is also no materialwastage as no trimming of edges is required. However, most of theconventional close-molded products still relies on the use of metals andplastics which are more costly and environmental unfriendly. Alternativemethods as described in patent publications WO2005/120787 andWO/2005/120967 have used wood fibers as a basic material to formmoldable mixture. These references use relatively high percentage ofwood fibers and use high percentage of Melamine Urea Formaldehyde as aliquid binder in their moldable mixture for molding their product. Theliquid binder used in their moldable mixture carries formaldehyde to themolded product which is known to be harmful to the environment andprobably harmful to our health. As a result, expensive exhaust systemsare required to eliminate the formaldehyde during processing under acontrolled environment.

The moldable mixture used in WO 2005/120787 and WO 2005/120967 alsorequire the use of soya extract as a de-molding agent for ease ofremoving the molded product from the mold, and the use of palm fibers asan impact modifier for providing a cushioning effect for the moldedproduct. The moisture content of the moldable mixture according to thesemethods is also relatively high because liquid binder is used. Theproducts molded with wood fiber usually have lower impact and bendingstrength because wood fibers are relatively brittle and difficult toflow. In order to produce product with the desired properties such ashigh impact and bending strength, high density, and more importantly thedesired profile, additional additives are used by these approaches toform the moldable mixture, and significant amount of liquid is alsoneeded to facilitate the flow of the moldable mixture in the mold so asto form the desired profile and strength.

The disadvantages of using large amount of liquid binder to facilitatethe flow of the moldable mixture in the molding process include: a) thehigh content of moisture vaporized during the molding process increasesthe pressure in the molding mixture which in turn increases the risk ofthe molded product being delaminated when the mold is opened because ofthe sudden release of pressure; b) the high water content in the liquidbinder may dilute the added adhesive to certain extend resulting inlonger molding time and therefore hardener which is for the accelerationof the hardening process is needed to ensure that the molded product isfully cured in the mold before it can be ejected out; c) the highpressure generated through the moisture/liquid vaporizing process maycause mold explosion if the pressure is not released in time. Pressurevents are therefore incorporated in the mold design which is tedious andexpensive; and d) the molded product produced with such process isusually prompt to fungus attack, and has relatively high shrinkage andthey warp easily due to high moisture content in the molded product; e)an additional ironing process by opening and closing the mold repeatedlyto allow the excess moisture/steam to escape during molding process isneeded so as to give sufficient time for the molded product to cure inthe mold before ejecting it out.

In addition, the methods disclosed in Patent Publications WO 2005/120787and WO 2005/120967 use ammonium chloride as a hardener to harden themolded product in the mold before it is ejected out because the moldablemixture had high moisture content. Hardening agent is easily hardened inhigh temperature and as such high temperature has to be avoided in theconventional molding process. On top of this, soya extract is also usedas the de-molding agent to facilitate the ejection process. The maindisadvantage of using soya extract is that the soya extract may notfacilitate the bonding among wood cells of the wood fibers. More liquidbinder is therefore needed to provide a desirable bonding property.However, the more the binder is used, the more the formaldehyde isemitted during the molding process.

Another alternative way to achieve a desirable molded product is to usea moldable mixture with low moisture content. However, it is difficultto mold a product with a complex profile if the moldable mixturecontains a material which is difficult to flow in the molding cavitywith low moisture content. In addition, the lower is the moisturecontent, the lower is the drawing ratio. The drawing ratio is an indexof how the moldable mixture can be flown in an enclosed mold.

In view of the afore-mentioned problems associated with the use of woodpallets, be it environmentally, health or cost, and all other alternatepallets available in the market, in one way or another has its ownshortcomings. It is therefore primarily important to come out with a newmoldable mixture which is free of formaldehyde and low in moisturecontent. Methods of manufacturing molded products and related partswhich are cost-effective, safe and capable of producing high density,light weight and more complex molded products are also important.

SUMMARY OF INVENTION

The first aspect of the present invention is to provide a moldablemixture containing at least one kind of agricultural fiber, a bindingagent that is substantially free of formaldehyde and a flow-promotingfiller material but in the absence of hardening agent, impact modifier,co-solvent and de-molding agent. The agricultural fiber may be rapestraw, rice stalk or a combination of both which contributes a largeportion in the mixture. The percentage weight of the agricultural fiberis between 85%-95% to the total weight of the moldable mixture. Theagricultural fiber of the moldable mixture has a moisture content ofless than 8% by weight to the moldable mixture. More preferably, themoisture content of such agricultural fiber is less than 5% by weight tothe moldable mixture. The small portion of the moldable mixture includesa substantially low percentage of binding agent which may be selectedfrom a formaldehyde-free class of chemical such asDiisocyanate-diphenylmethane (MDI) or any soy-based binding agent. Thepercentage weight of the binding agent in a preferred embodiment is notmore than 5% to the total weight of the moldable mixture. Such class ofchemical can be mixed well with the agricultural fiber and improving thepacking of agricultural fiber in the moldable mixture. A substantiallylow percentage of flow promoter which is also used as the fillermaterial is also added such as wheat flour to mix with agriculturalfibers to promote the flow of the moldable mixture, and at the same timefill up the empty space between the fiber cells during molding. Thepercentage weight of the flow-promoting filler material in a preferredembodiment is less than 10% by weight to the moldable mixture. Themolded product with the use of flow-promoting filler material isrelatively much compact and it is not prompt to absorb moisture from airfreely and hence it is less prompt to warp, shrinkage and fungus attack.One distinguishing feature of the present invention is the absence ofhardener, impact modifier, de-molding agent and co-solvent in themoldable mixture. The moisture content of the moldable mixture of thepresent invention is also relatively low because not more than 5% byweight of the high viscosity binder is used and the nature of suchbinder is low in moisture content. The components for the moldablemixture of the present invention are easily accessible, simple andcost-effective. In summary, the key features of the moldable mixture inthe present invention are:

Free of Formaldehyde. Not more than 5% by weight of high viscositybinder, especially Diisocyanate-diphenylmethane (MDI) or any soy-basedbinding agent, is added as a component of the moldable mixture. The useof this high viscosity binder can keep the total moisture content of themolding mixture relatively low.

Wheat Flour is used instead of Tapioca Flour. This is mainly due to thefact that Tapioca Flour is much costly and it is gluten-free. As tapiocaflour is gluten-free, products produced are therefore much brittle. Onthe other hand, wheat flour contains proteins called gluten. When moldedproducts made with wheat flour is kneaded, the gluten moleculescross-link to form a sub-microscopic network that gives the product anelastic structure. This allows the retention of gas bubbles in an intactstructure, resulting in an aerated final product with a ductile texture,and the product produced is therefore less brittle.

No de-molding agent material such as soya extract and hardener such asammonia chloride are added to form the moldable mixture. The mold iscoated with a layer of commercially available de-molding material andwith the hydraulic ejection system incorporated in the mold and pressdesign, and also due to the fact that the moisture content of themoldable mixture is relative low (as no more than 5 wt % of highviscosity binder, especially MDI or any soy-based binding agent isused), the molded product can be ejected out from the mold easily. Nohardener such as ammonium chloride and de-molding agent such as soyaextract are added to form moldable mixture. The molded product takes amuch shorter time to cure in the mold due to less moisture content. Inaddition, no co-solvent such as alcohol is added to facilitate thecuring process in the present invention, whereas co-solvent is used toaccelerate the vaporization process of the moisture in the moldablemixture when the moldable mixture used is in high content of moisture.

Relatively Light weight. Agricultural fibers such as rape straw and/orrice stalk are used as the basic materials. These materials are almostone-third lighter than wood or wood related materials.

The second aspect of the present invention relates to methods ofmanufacturing molded products and related parts including steps ofproviding the materials agricultural fibers, a binding agent and aflow-promoting filler material for a moldable mixture, mixing theprovided materials to form a moldable mixture, shaking the moldablemixture in preparing for compression molding and compression molding themoldable mixture to form a molded product.

Distinguishing features of the present invention from conventionalmolding process include a different composition and moisture content ofthe moldable mixture during the providing step, a shorter and moresimple mixing and molding cycle during the mixing step, a more evenlydistributed and right amount of moldable mixture during the shakingstep, a higher draw ratio of moldable mixture due to the use offlow-promoting filler material during the molding step, the absence ofheat treatment and fumigation after molding step, and a higher densityand lighter weight with greater range of thickness of the molded productcan be molded.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 shows the flow chart of manufacturing a close-molded product.

FIG. 2 is an illustration of a device for shaking the moldable mixturethroughout the discharging of the moldable mixture from IBC untilloading the moldable mixture into a mold.

FIG. 3 shows the top and bottom views of the material feeding tray usedin the shaking step.

FIG. 4 is an enlarged image of the material feeding tray showing anadditional vibrator in each corner for shaking the moldable mixtureduring the shaking step.

FIG. 5 shows the design of the material feeding tray with shakingfeatures in the present invention (lower part) for loading the moldablemixture to the bottom mold at the pressing area as compared to thedesign of the conventional material feeding tray (upper part) withoutshaking features.

FIG. 6 is an enlarged image of the mold and the hydraulic press at thepressing area in the molding step.

FIG. 7 shows the cross-section of the top and bottom mold with themoldable mixture before and after compression in the molding step.

FIG. 8 shows the side-prospective view of a molded pallet of the presentinvention.

DETAILED DESCRIPTION OF INVENTION

In FIG. 1, the claimed methods of manufacturing molded products andrelated parts are mainly arrived by four steps including a providingstep (100), a mixing step (120), a shaking step (140) and a compressionmolding step (160). In the providing step, agricultural fibers providedto form a moldable mixture may be rape straw, rice stalk or acombination of both. In one embodiment, the raw materials ofagricultural fiber have to be trimmed to a length ranges from 5 to 10 mmin a trimming step (not shown) prior to mixing with other components toform a moldable mixture. The trimmed raw agricultural fibers are thendried in a drying step (not shown) to have less than 8% moisture contentto the total weight of the moldable mixture, preferably have less than5% moisture content to the total weight of the moldable mixture. Thedrying step of the raw materials of the agricultural fiber is followedby a weighing step (not shown) to weigh a suitable amount ofsubstantially dry agricultural fiber prior to mixing with othercomponents to form the moldable mixture. In one embodiment, thepercentage by weight of the substantially dry agricultural fiber isbetween 85%-95% to the total weight of the moldable mixture. In theproviding step, a binding agent is also provided to form the moldablemixture. In one embodiment, the binding agent isDiisocyanate-diphenylmethane (MDI). Alternatively, the binding agent canbe any soy-based binding agent. In one embodiment, soy-based bindingagent used in the moldable mixture may be soy flour. The percentage byweight of the binding agent is not more than 5% to the total weight ofthe moldable mixture. This binding agent is high viscosity, low inmoisture content and free of formaldehyde. In the providing step, aflow-promoting filler material is also provided to form the moldablemixture. In one embodiment, the flow-promoting filler material is wheatflour. The flow-promoting filler material is less than 10% by weight tothe moldable mixture. In a preferred embodiment, three main materialsincluding agricultural fibers, a binding agent and a flow-promotingfiller material are provided in the providing step to form a moldablemixture, but hardening agent, impact modifier, co-solvent and ade-molding agent are not provided in the same providing step. In oneembodiment, hardener such as ammonium chloride, de-molding agent such assoya extract, co-solvent such as alcohol, and impact modifier such aspalm fibers are not provided in the providing step to form a moldablemixture.

In FIG. 1, after weighing the substantially dry agricultural fiber in aweighing step (not shown), 85%-95% by weight of the substantially dryagricultural fiber such as rape straw, rice stalk or a combination ofrape straw and rice stalk is mixed with other components to form amoldable mixture in a mixing step (120). In one embodiment, the mixingstep is a two-step mixing step. In the first part of the two-step mixingstep, 85%-95% by weight of the substantially dry agricultural fiber ismixed with less than 10% by weight of a flow-promoting filler materialsuch as wheat flour in a mixing machine (not shown). In one embodiment,the mixing machine comes with a horizontal rotating blade (#4 bladesmounted on horizontal shaft) and it is rotating at about 20 to 30 rpm.While the agricultural fiber is stirred in the mixing machine, the wheatflour of less than 10% by weight is introduced to the stirringagricultural fiber in the first part of two-step mixing step. In thesecond part of the two-step mixing step, not more than 5% by weight of abinding agent such as Diisocyanate-diphenylmethane (MDI) or anysoy-based binding agent is also introduced to the mixing machine byspraying (not shown). In one embodiment, not more than 5% by weight ofMDI is sprayed with a pressure nozzle at a pressure of around 5 to 8bars into the stirring mixture of agricultural fibers and aflow-promoting filler material. In another embodiment, not more than 5%by weight of soy-based binding agent such as soy flour is sprayed with apressure nozzle at a pressure of around 5 to 8 bars into the stirringmixture of agricultural fibers and a flow-promoting filler material. Inthe mixing step, the mixture of agricultural fibers, a flow-promotingfiller material and a binding agent is kept stirring until such mixtureis blended to form a moldable mixture. In one embodiment, the wholerotating cycle for a mixing step takes less than 3 minutes.

In FIG. 1, upon completion of the mixing step (120), the moldablemixture is ready for feeding the moldable mixture to the mold in ashaking step (140). In the shaking step, the moldable mixture is loadedinto an Intermediate Bulk Container (IBC) (not shown) and thendischarged through the weighing Hopper (not shown) into a materialfeeding tray at the material loading station (not shown). The materialfeeding tray filled with moldable mixture is then transferred from thematerial loading station to a pressing area (not shown) wherecompression molding (160) takes place. In one embodiment, the moldablemixture has been shaking throughout the discharging of the moldablemixture from IBC through the weighing hoop into the material feedingtray. In another embodiment, the material feeding tray containing themoldable mixture has also been shaking throughout the loading of themoldable mixture from the material feeding tray to the cavity of thebottom mold at the pressing area where compression molding takes place.

In FIG. 1, after shaking (140) the moldable mixture, the moldablemixture is ready for being compressed in a compression molding step(160). The compression molding step is performed at a single compressionstroke. In one embodiment, the compression molding step is carried outat a temperature between 200-230° C. In one embodiment, the mold isheated up through internal heat transfer at a temperature between200-230° C. The moldable mixture is compressed under a pressure between0.30 to 0.40 kg/mm² for 1.5 to 2.5 minutes. After compression molding,the molded product is ejected out from the mold and then transferred toa packing area next to the pressing area. The molded product is notsubjected to heat treatment and fumigation for killing any living pestsafter ejecting out from the mold.

An example of mixing and shaking the moldable mixture is given in FIG.2. In this example, the Intermediate Bulk Container (IBC) (81) is placedat the top of a stand-alone material loading station (85). The moldablemixture (not shown) may be discharged through a discharging screw (notshown) into a weighing hopper (82) and then further discharged into amaterial feeding tray (83) in a row-by-row manner. After the completionof the discharging, the material feeding tray is then transferred alongthe tray movement path (84) to the pressing area (88) where thecompression molding step takes place. The moldable mixture beingtransferred into the mold (87) at the pressing area is compressed by thehydraulic press (86) into the molded product.

An example of a material feeding tray is given in FIG. 3. In thisexample, the top view of the material feeding tray (310) shows that itmay have an average size of 1.4×1.2×0.2 meter (Length×width×height) andmay be divided into 35 to 49 compartments to cater for the loading ofdifferent weight of moldable mixture for molding into product withdifferent profile and thickness at different part of the product. Eachcompartment (320) is designed to take different weight of moldablemixture. This is to ensure that the right amount of the moldable mixtureis loaded evenly into the mold at the pre-determined position foroptimum molding result and material utilization. It also helps tofacilitate the molding process to provide with the maximum draw ratioand enables to mold products with different profile and thickness atdifferent sections of the product. The combination of compartmentsvaries from the complexity and the size of the molded product. In orderto facilitate the flowing of the agricultural fibers in a mold duringthe molding step, the partitions of the material feeding tray areconstructed by steel sheet (not shown) in a criss cross manner to formthe necessary compartments.

The example as given in FIG. 3 shows that the bottom view of thematerial feeding tray has a piece of wire mess (330) welded at thebottom face of the steel partitions. The entire steel partition isconnected to a rotating rod with a vibrator mounted (not shown). Thesteel partition together with the welded wire mess can be used forshaking in the horizontal direction throughout the discharging of themoldable mixture, from the material feeding tray to the mold at thepressing area (not shown). The gate (340) mounted at the bottom of thematerial feeding tray is then opened by sliding movement in thehorizontal direction when the material feeding tray is transferred tothe mold at the pressing area.

On top of the welded wire mesh, four additional vibrators (410) as shownin FIG. 4 are mounted at the four corners of the material feeding traywhich are also shaking concurrently in the vertical direction throughoutthe discharging and loading of the moldable mixture.

In the lower part of FIG. 5, the moldable mixture (530) is dischargedinto the cavity of the bottom mold (560) in an evenly dispersed mannerwith the aid of both the horizontal and vertical vibration motionsgenerated by the rotating rod with a vibrator (not shown in FIG. 5) andfour additional vibrators at four corners of the material feeding tray(550) as described above prior to the compression molding step. Thiskind of shaking feature is incorporated in the present invention due tothe fact that when using the conventional method, the loading ofmoldable mixture from the conventional material feeding tray (510) intothe bottom mold without any shaking always forms a hump (520). On theother hand, the material feeding (540) of the present invention has tobe leveled by four additional vibrators at four corners of the bottomside (550) to enable shaking when loading the moldable mixture from thematerial feeding tray into the bottom mold at the pressing area. Suchfeature can achieve the effect of optimum molding results, i.e. minimummolding pressure, minimum material use. Such feature also enables themoldable mixture to flow freely to the desired height which can bedetermined by the draw ratio. After the moldable mixture is fully loadedinto the cavity of the bottom mold, the material feeding tray may bereturned to the original position for re-filling.

An illustration of a hydraulic ejection system for molding is given inFIG. 6. In this example, the hydraulic ejectors (630) are situated belowthe bottom mold at the pressing area. In one embodiment, the moldablemixture is molded at a pressing area at a temperature between 200-230°C. Both the top (610) and bottom (620) mold are fitted with varioussteel pipes (not shown). The thermal oil is electrically heated andcirculating through the oil channels inside the mold. Since the mold isheated up through heat transfer within the mold, therefore it canachieve a lower energy loss.

In one embodiment, the moldable mixture is compressed under a pressurebetween 0.30 to 0.40 kg/mm² for 1.5 to 2.5 minutes at the pressing area.The compression molding is performed as a single compression stroke.There is no need to open and close the mold repeatedly nor ironing torelease excess moisture to prevent possible mold explosion because themoldable mixture of the present invention has relatively low moisturecontent. After the compression, the molded part is ejected out from thebottom mold with the hydraulic system (630). A mechanical pick and placesystem (not shown) is incorporated in the material feeding system topick up the molded part and transfer the molded part to a packing area(not shown) next to the pressing area. Since the molded product has beensubjected to high heat and high pressure during the molding process,further heating and fumigation steps for killing living pests in themolded product are not required.

FIG. 7 illustrates the cross-section of a molding part in the moldbefore and after the compression in the molding step. The upper part ofthe figure shows the cross-section of the moldable mixture (720) in thecavity of bottom mold (740) before the compression molding step whereasthe lower part of the figure shows the cross-section of part of themolded product (760) in the cavity between the top mold (780) and thelower mold (790) after the compression molding step. In one embodiment,the top mold (780) is pressed on the moldable mixture in the cavity ofthe bottom mold (790) with a pressure of 0.30 to 0.40 kg/mm² to formmolded product (760). The compression molding for the moldable mixtureinto part of a molded product is a single compression stroke without theneeds of opening and closing the mold repeatedly. In one embodiment, themoldable mixture after the compression flows upwards towards thehorizontal molding cavity of the enclosed mold under the temperaturebetween 200-230° C. The height (750) of part of the molded product (760)along the horizontal molded cavity of the enclosed mold can bedetermined. The draw ratio of the moldable mixture is obtained fromdividing the height (750) of the molded part (760) in the horizontalmolding cavity of the enclosed mold after compression by the height(710) of moldable mixture (720) in the cavity of bottom mold (740)before compression. Such ratio reflects the upwards flowing ability ofthe moldable mixture during molding.

Due to the high draw ratio and high density, the molded part can becorrugated with complex profile such as runner (810) and plank (820) ofa pallet (830) as shown in FIG. 8. The molded product is ready for useor can be used repeatedly without any post-heat treatment andfumigation.

While the present invention has been described with examples topreferred embodiments, it will be apparent that other changes andmodifications could be made by one skilled in the art, without varyingfrom the scope or spirit of the claims appended hereto.

INDUSTRIAL APPLICABILITY

The present invention provides a moldable mixture and methods ofmanufacturing molded products and related parts based on the claimedmoldable mixture. The claimed moldable mixture can be applied to thefield of construction materials and manufacture of molded products suchas pallets and related parts. The claimed methods of manufacturing canbe applied to making construction products or molded products withbetter quality.

We claim:
 1. A moldable mixture comprising a binding agent, aflow-promoting filler material and an agricultural fiber, wherein saidmoldable mixture is in the absence of hardener, impact modifier,co-solvent and de-molding agent.
 2. The moldable mixture of claim 1,wherein said binding agent is Diisocyanate-diphenylmethane with anamount not more than 5% by weight to said moldable mixture.
 3. Themoldable mixture of claim 2, wherein the said binding agent issubstantially free of formaldehyde.
 4. The moldable mixture of claim 1,wherein said agricultural fiber is at least one agricultural fiberselected from a group consisting of rape straw and rice stalk.
 5. Themoldable mixture of claim 4, wherein said agricultural fiber is between85% to 95% by weight to said moldable mixture.
 6. The moldable mixtureof claim 1, wherein said flow-promoting filler material is wheat flourwhich is less than 10% by weight to said moldable mixture.
 7. Themoldable mixture of claim 1, wherein said binding agent is a soy-basedbinding agent with an amount not more than 5% by weight to said moldablemixture.
 8. A method of manufacturing a molded product comprising thesteps of: a. Providing an agricultural fiber, a binding agent and aflow-promoting filler material; b. Mixing said agricultural fiber withsaid flow-promoting filler material and said binding agent to form amoldable mixture; c. Shaking said moldable mixture in preparation forcompression molding; d. Compression molding said moldable mixture toform molded product.
 9. The method of claim 8, wherein said mixingfurther comprises spraying said binding agent at pressure between 5 to 8bar into said agricultural fiber with said flow-promoting fillermaterial, wherein said binding agent is Diisocyanate-diphenylmethanewith an amount not more than 5% by weight to said moldable mixture. 10.The method of claim 8, wherein said binding agent is a soy-based bindingagent with an amount not more than 5% by weight to said moldablemixture.
 11. The method of claim 8, wherein said agricultural fiber isat least one agricultural fiber selected from a group consisting of rapestraw and rice stalk.
 12. The method of claim 8, wherein saidagricultural fiber is between 85% to 95% by weight to said moldablemixture.
 13. The method of claim 8, wherein said flow-promoting fillermaterial is wheat flour which is less than 10% by weight to saidconstruction molding mixture.
 14. The method of claim 8, wherein saidmixing takes place in the absence of hardener, impact modifier,co-solvent and de-molding agent.
 15. The method of claim 8, wherein saidshaking further comprises discharging said moldable mixture from amaterial loading station into a material feeding tray with a shakingmotion.
 16. The method of claim 15, wherein said discharging is followedby transferring said moldable mixture from said material feeding tray toa mold with a shaking motion in preparation for compression molding. 17.The method of claim 8, wherein said compression molding is performed asa single compression stroke.
 18. The method of claim 17, wherein saidsingle compression stroke is performed with a draw ratio from 1 to 10.19. The method of claim of 8, wherein said compression molding isperformed at a temperature from 200 to 230 degree Celsius.
 20. Themethod of claim of 8, wherein said compression molding is performed at apressure from 0.30 to 0.40 kg/mm².